The present invention relates to a method and apparatus for the reproduction of an image which involves the formation of an image on a recording member using electrical signals and more particularly relates to the formation of a recording element which can be utilized to project a positive or negative photographic image.
Materials known as "electret" are those prepared by maintaining a film, sheet or other shaped particle of a plastic composed of a polymeric or organic material such as carnauba wax or naphthalene; a polar resin such as polyfluorovinylidene resin, a polyvinyl chloride resin, polycarbonate, polyester, and acrylic resin, etc.; a non-polar resin such as polyethylene, polypropylene, polystyrene, etc. or copolymers of them; or a mixture of these materials at a suitable temperature for a period of time under the application of a D.C. potential and cooling the article to room temperature while maintaining the D.C. potential, resulting in the electrical polarization of the material in the direction of the applied D.C. potential.
Heretofore, such electrets have been composed of materials which afford excellent workability, toughness and flexibility for use in transformers such as speakers and microphones. It is known to use electrets in the production of electrostatic images in which a photoemissive layer is deposited on a charged electret after which an image is projected into the layer forming an electrostatic latent charged image after which it is developed to become visible. An example of this type of process may be found in U.S. Pat. No. 3,007,735. The disadvantage of this method of producing images is the expense involved, and further that it is limited to the production of either a photographic positive or a negative image, but not both within the same film. It is therefore a principal object of this invention to produce a photographic storage element which may project a positive or negative photographic image. It is a further object of this invention to provide a low-cost method of producing such a photographic element.